It's counterintuitive that you need to unquote Google App Engine URL parts twice.

delete index: google app engine

appcfg.py vacuum_indexes ./

Google App Engine Data Migration: Deleting an attribute

One can:

1. Change the model class definition so that it extends Expando.
2. Remove the undesired attribute from the property definition list.
3. Add code which calls del mymodel.myattribute on all the entities eventually
4. Change the model class definition back to Model

Google App Engine appcfg.py update error:

Could not guess mimetype for favicon.ico. Using application/octet-stream.

Solution:

Add mime_type: image/vnd.microsoft.icon to the appropriate part of app.yaml

Serializing to JSON with Google App Engine

from django.utils import simplejson

Then: http://simplejson.googlecode.com/svn/trunk/docs/index.html